Process of producing alkali metal salts of nitrilotriacetic acid



Patented Mar. 10, 1953 2,631,165

.PRo'oEss-pr PRODUCING .ALKALI "METAL 10F NITBJLOTRIACETIC ACID it-Claims. (Cl. 260-534) "The'presentinvention relates to a new and boiling or by -combining both :measures. 'lhe useful method-.ofproducing-alkali metal salts of "formaldehyde is added i-n l's'uch'f-a ima'nner and nitrilotriacetic acid. under such 'conditions of working "that fit @ca'nwhereas'there iexis'twariousme'thods ofqpronot react with ammonia itself. 'Ihis mztybe ducing t e said salts it has now been found *5 f c d by'W l; t' a' Pe that theyamayhe,producedaccording.to the preseffects the "immediate escape :of Iammonia rand ent invention in'a" mannersuperior to any other water. Reduced "pressure, for example a -vacumethod: so far known. um of from to 200' millimeters, may "also-serve Itis :an object of this invention to provide this purpose, thetemperature being lower, :for

aentirelynew and valuable means of producing in example between 40 and 60 C. -the alkali-metalsalts ofi.nitrilotriacetic acid. It According to this new method "aqueous soluis a further object of this invention to obtain tion's of alkali metal salts of mtr-ilotriace'etic acid the said salts-in-.-astate in-which they may be are obtained :inexcellentyields. Theyr-may be usedimmediately for commercial purposes, such employed as such or, *after evaporation of waa's softeninghardwater. '15 t'er, in the form of*the'f'correspondingsolidsalts,

In performing the new process, alkali -metal for example*as-Tsofteningagentsiforwater.

cyanides are reacted with ammonia and formal- The following examples will further illustrate dehyde in an alkaline medium under such condihow this invention may be carried out in practions that the ammonia is substantially retained tice. The invention, however, is not limited to in the reaction medium, and after this reaction 2 these examples. The parts are by weight. the ammonia is removed and the resulting liquid is reacted with an alkali metal cyanide and form- Example 1 aldehyde Whlle heetmg e remo'vmg the e A mixture of 366 parts of 27.8 per cent aqueous monia formed during this stage of the reaction. ammonia and 534 parts of a 28 per cent aqueous Any alkali metal cyamdes may be used for the solution of sodium cyanide is added to 24 parts purpose of thls reeenen- Whereas I prefer the of a 50 per cent sodium hydroxide solution and use P Sodium e Potassium e e then mixed with 300 parts of 30 per cent aqueous cyamdes of other alkali metals, such as lithium, form ld h de After mixing the reactants, the

m y a be p y reaction takes place under evolution of heat. It

The first stage of the a t as descllbed 30 is completed while boiling the mixture for about ab v ay be earned Out either in a closed half an hour under reflux and further heating unsel or u d r reflux OOOImg- The reactlon der distilling off the vapors until the liquid no preferably carried out at elevated temperature. longer contains any ammonia. Then 178 parts The p a e range for working unde of a 28 per cent aqueous sodium cyanide solumel p e y l b w about and tion are added. The liquid is now heated under for Working under reduced pressure, reduced pressure (12 millimeters) at from 40 e. g. at 12 or 15 millimeters, between about 40 t 60 (3,, and 100 parts of a 30 per cent aqueous and 60 C. The a ali m t yanide and the formaldehyde solution are slowly allowed to flow formaldehyde are employed in about equivalent drop by drop into the mixture. The liquid is then amounts. The amount of ammonia, however, 40 further heated for another 30 minutes at the said may be varied within wide limits. For example, temperature. The addition of the amounts of the quantities employed may be between 0.1 and sodium cyanide and formaldehyde stated above 3 molecular proportions calculated with respect is repeated until 1070 parts of the cyanide soluto the alkali metal cyanide or formaldehyde tion and 600 parts of the formaldehyde have respectively. As soon as the initial quantities been added. In this manner 1800 parts of an of alkali metal cyanide and formaldehyde are about 36 per cent solution of the sodium salt of completely reacted forming the corresponding nitrilotriacetic acid are obtained, corresponding alkali metal salts of amino-mono, -diand -trito a yield of about 95 per cent.

acetic acids, the reaction mixture is freed from any ammonia still present, for example by heat- Example 2 i if desired, under reduced Pressure In A mixture of 197 parts of a 31 per cent aqueous a second stage the solution freed from ammonia potassium cyanide solution and 136 parts f 25 is reacted With from 3 to 10 times the amounts per cent aqueous ammonia is rendered more of alkali metal cyanide and formaldehyde used strongly alkaline by adding 8 parts of a 50 per in t e i tia St o the reaction in Such a cent potassium hydroxide solution. To the mix manner that the ammonia formed by the saponiture 120 parts of 25 per cent aqueous formaldefication of the nitriles formed as intermediate hyde are added while cooling under reflux. The products is removed as quickly and completely mixture which initially develops heat is, after :as possible, for example by carrying out the the addition of formaldehyde, boiled for an hour process under reduced pressure or by heating to under reflux, then freed fromammonia by distillation and then again mixed with 197 parts of a 31 per cent potassium cyanide solution. While continuously distilling off ammonia and water, further 120 parts of a 30 per cent aqueous formaldehyde solution are allowed to flow drop by drop into the solution which is continuously kept boiling. The addition of the potassium cyanide solution and formaldehyde in the same amounts is repeated after half an hour of distillation. In this manner, 860 parts of a 30 per cent aqueous solution of the potassium salt of nitrilotriacetic acid are obtained corresponding to a yield of 84 per cent of the calculated yield.

I claim: k 1. A process of producing alkali metal salts sof nitrilotriacetic acid which comprises reacting Jan alkali metal cyanide with ammonia and formaldehyde in an alkaline medium under such conditions that the ammonia is substantially re- .tained in the reaction medium, removing the ammonia aiterthis reaction, and reacting the resulting liquid with an alkali metal cyanide and formaldehyde while heating and removing the ammonia as formed during this stage of the reaction.

2. A process of producing the sodium salt of nitrilotriacetic acid which comprises reacting sodium cyanide with ammonia and formaldehyde in an alkaline medium under such conditions that -.the ammonia is substantially retained in the reaction medium, removing the ammonia after this reaction, and reacting the resulting liquid with sodium cyanide and formaldehyde while heating and removing the ammonia as-formed during this stage of the reaction.

. 3. A process of producing the sodium salt of nitrilotriacetic acid which comprises reacting sodium cyanide with ammonia and formaldehyde in an alkaline medium under such conditions that the ammonia is substantially retained in the reaction medium, removing the ammonia after this reaction, and reacting the resulting liquid with sodium cyanide and formaldehyde while heating and removing the ammonia as formed during this stage of the reaction under reduced pressure.

ERNST PLOE'ITZ.

REFERENCES CITED The following references are of recordin th file of this patent:

'UNITED STATES PATENTS Number Name Date 2,168,181 Ulrich et a1. Aug. 1, 1939 2,407,645 Bersworth Sept. 1'7, 1946 2,461,519 Bersworth Feb. 15, 1949 2,500,019 Bersworth Mar. 7, 1950 OTHER REFERENCES Polstorii et al., Ber. DeutuChem vol. 45, pp. 

1. A PROCESS OF PRODUCING ALKALI METAL SALTS OF NITRILOTRIACETIC ACID WHICH COMPRISES REACTING AN ALKALI METAL CYANIDE WITH AMMONIA AND FORMALDEHYDE IN AN ALKALINE MEDIUM UNDER SUCH CONDITIONS THAT THE AMMONIA IS SUBSTANTIALLY RETAINED IN THE REACTION MEDIUM, REMOVING THE AMMONIA AFTER THIS REACTION, AND REACTING THE RESULTING LIQUID WITH AN ALKALI METAL CYANIDE AND FORMALDEHYDE WHILE HEATING AND REMOVING THE AMMONIA AS FORMED DURING THIS STAGE OF THE REACTION. 